Report on Queen Conch (Lobatus gigas) Population Monitoring in Lac Bay 2020

Historical Data

A study conducted in 1969 by Hummelinck and Roosgave the first qualitative data forqueen conch general distribution throughout Lac Bay. In 2000, a study by Lottpresented the first quantitative data within the same study area. This was followed by asecond survey in 2007. From 2010 onwards (Conch Stock Restoration Project)assessment of queen conch population has been done at irregular intervals (2010,2013, 2015, 2016, 2020).

A total of 43,200 m2 was surveyed and 85 live conchs were found and measured. This resulted in a population density of 19.27 conchs / Ha. To use the Allee effect, only sexually mature conchs should be considered. Over the course of this study, no sexually mature conchs were found , the oldest conch had a lip thickness which measured 6 mm.

Below, Table 1 has been included to summarize the results of the last 5 surveys (2010, 2013, 2015, 2016, 2020). It is interesting to note the dramatic increase between conch populations in 2010 and 2013, and then the rapid decrease in follow on surveys. The results of the 2020 survey highlight a significant issue with only 85 conchs found, none of which having reached sexual maturity. Figure 4 shows a map with the total number of live conchs found per location. There was also a significant number of poached conchs (Table 2/Figure 5) found within the bay. In fact, there were more poached conch shells (100) found than live conch (85), demonstrating that poaching is still an issue which needs to be addressed before the conch population can rebound. 

Each quadrant (quantity 49) equates to 0.09 ha. Using this value, the following densities per year were calculated: 2010 (6.35 conchs/ha), 2013 (51.70 conchs/ha), 2015 (46.49 conchs/ha), 2016 (21.54 conchs/ha), 2020 (19.27 conchs /ha) 

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